The present invention is directed to an extruded multiwall tubular structure having internal helical forms, and an apparatus and method for forming an extruded multiwall tubular structure having internal helical forms.
Conveyor systems are widely used within industry to transport raw materials, components and/or finished products along an assembly line or otherwise within or between manufacturing facilities. One common conveyor system is a belt driven roller conveyor system. In belt-drive roller conveyor systems, a moving belt is raised or lowered beneath a set of elongated cylinders (i.e., rollers) to make or remove contact between the moving belt and the rollers. When the moving belt contacts the rollers, the rollers rotate in the opposite direction as the belt. As a result, a bale of goods or other article situated on top of the rollers is conveyed along the conveyor path as the rollers rotate in place. Other roller conveyor systems are known, including gravity and chain driven systems.
Unfortunately, numerous drawbacks are associated with conventional roller conveyor systems. Among those disadvantages include that the systems are often labor-intensive to install and maintain. Because they are often used continuously in a manufacturing or warehouse environment, roller conveyor systems can be subjected to long and rigorous operating conditions, resulting in wear and tear of components that require frequent maintenance. Maintenance of roller conveyor systems is often expensive, due in large part to the procurement and installation of spare parts, many of which are heavy and cumbersome.
Still other drawbacks not adequately addressed with known roller conveyor systems relate to safety. For example, individuals cannot cross a roller conveyor system without risk of falling onto the rollers, which can spin freely underfoot as one tries to walk across them. However, the alternative, walking entirely around the roller conveyor system, is not efficient, particularly since roller conveyor systems can extend for tens of yards or more.
These and other drawbacks are found in current roller conveyor systems.
While not limited to cylindrical rollers of roller conveyor systems, it would be desirable to manufacture hollow tubular or cylindrical components with a structural reinforcement member arranged helically between inside and outside tube walls, which would offer enhanced structural strength and rigidity, as well as reduced weight. Not surprisingly, there are many functions in industry for an internally located helix within a tube or cylinder. In addition, it is also desirable to affix to the outside geometry of a tubular component other helical forms such as a single inside diameter (ID), multiple inside diameters (ID's), ribs, gear teeth, bearing grooves, splines, fins, oil grooves or the like. Unfortunately the manufacturing of these items is labor intensive and is done in multistage processes that adds cost and time to original equipment manufacturers (OEM's) who use these items as sub-assemblies and components of their finished goods.
Because tubes or cylinders with helical reinforcement members are used in many different consumer and industrial applications, the manufacturing of these items has already been established, but has always been done in a multistage manufacturing process. Attempts to minimize this to a single stage application or process via means of injection molding, die casting, or investment casting have all been cost prohibitive, limited based on size constraints and/or limited as to usable materials. Even traditional extrusion processes, which use a simplified mold with an external puller that would simultaneously pull and twist the extruded material has not proven capable of producing this arrangement due to torque requirements and end production quality concerns.
It would be desirable in the art for a roller conveyor system apparatus and method of extrusion of tubular outside geometries having internal helical forms, and the extruded multiwall tubes having internal helical forms produced by such an apparatus and method, such as usable for manufacturing conveyor rollers without the above-mentioned drawbacks.